Corona cap



y 1969 E. L. ELDRIDGE 3,458,646

' CORONA CAP Filed Feb. 27, 1968 2 Sheets-Sheet 1 FIG. 1

PRIOR ART INVENTOR.

EDWARD 1.. ELDRIDGE ATTORNEY July 29, 1969 L ELDmDGE 3,458,646

CORONA CAP Filed Feb. 27, 1968 Z SheetS-Sheet 2 INVENTOR.

EDWARD L. ELDRIDGE FIG 9 A T TORNE Y United States Patent US. Cl. 17473 2 Claims ABSTRACT OF THE DISCLOSURE The disclosure is directed to a corona cap to prevent the formation of corona about the rough irregular couplings of high potential conductors by providing a smooth, regular cap therefor. The corona cap consists of a base member and two, or four, side members forming a circular or generally rectangular box and stand off supports connected to either the side members of the cap or to the corners of the side members and placed in contact with the connector itself. A bolt is then positioned in an indented recess and bolted to the connector itself.

BACKGROUND OF THE INVENTION Field of the invention The invention is directed to the field of high potential conductor transmission and distribution systems wherein the connectors provide relatively uneven projections from the connectors which would greatly increase the potential of corona. Although applied generally to the field of transmission and distribution equipment, the invention finds use in any area wherein high potential conductors are employed and which is subject to corona.

Description of the prior art Spherical corona caps are known in the prior art for connection at the point where conductors of different diameters are joined. Such a device is shown in the Harmon Patent No. 3,046,327. Further, corona caps have been employed as part of the terminal, or connector, itself as is shown in Mankin Patent No. 2,434,572 and Zelt Patent No. 2,786,883. However, in these embodiments the corona shield is formed as a part of the connector itself and is limited to the specific application shown. No form of corona cap is known of which will find utility for the protection of bolted connections of high potential conductors as is described in the instant invention.

SUMMARY OF THE INVENTION The invention is directed to a corona cap for use at the bolted couplings, or connectors, of high potential conductors. The corona cap permits the simple protection of existing, or newly installed, high potential conductor connectors and may be field installed. The corona cap is fabricated from a base member and two, or four, side members arranged to form a protective shield for the otherwise exposed ragged ended, sharp edged bolt and nut couplings. Stand off supports are provided for the corona cap in order that the cap may be spaced from the coupling to permit the escape of moisture, collected within the corona cap, thus decreasing the potential for corona. It is therefore an object of this invention to provide a corona cap to provide a smooth continuous surface to prevent corona at bolted high potential conductor connectors.

It is still another object of this invention to provide a corona cap having stand off supports whereby the main portion of the corona cap is held apart from the connector thus providing for the easy removal of moisture collected within the corona cap.

It is yet another object of this invention to provide a 3,458,646 Patented July 29, 1969 corona cap which may be easily installed in the field with a minimum of additional installing equipment.

Other objects and features of the invention will be pointed out in the following description and claims and BRIEF DESCRIPTION OF THE DRAWINGS In the drawings FIG. 1 is a side elevation of a typical, dead and coupling for high potential conductors and showing the manner in which the connectors are connected by means of nut and bolt arrangements.

FIG. 2 is a bottom plan view of a first embodiment of a corona cap constiucted in accordance with the concepts of the invention.

FIG. 3 is a side elevation, in section, of the corona cap of FIG. 2 taken along the lines 3-3.

FIG. 4 is a side elevation of the corona cap of FIG. 2 installed upon the connector of FIG. 1.

FIG. 5 is a side elevation, in section, of a corona cap in a position similar to FIG. 4.

FIG. 6 is a bottom plan view of a further embodiment of the corona cap constructed in accordance with the concepts of the invention.

FIG. 7 is a side elevation, in section, of a corona cap according to FIG. 6 shown along the lines 7-7.

FIG. 8 is a side elevation of a substation distribution network in which a feeder cable is connected to a bus bar and the nut and bolt assembly is protected by corona caps on both the nut side and bolt side.

FIG. 9 is a front elevation of a further corona cap constructed in accordance with the concepts of the invention;

Similar elements are given similar reference characters in each of the respective figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to FIG. 1 there is shown a typical dead end connector feeder line as employed with high potential conductors. Dead end 10 is coupled to a conductor 12 at a first end thereof and is coupled by means of a loop 14 to a series of insulators'16. The insulators in turn are connected to a support cable 18 which in turn may be connected to a supporting structure (not shown). Dead end 10 also includes a terminal pad 20 which is bolted by means of a nut 22 and bolt 21 arrangement to a tap line 24 composed of the connector 26 and a conductor 28. As can be seen from the figure, the bolt 21 and nut 22 arrangement uses generally hexagonal bolts 21 having relatively sharp edges and also a portion of the bolt 21 itself extends beyond the nut 22 providing additional sharp edged portions. It has been found, in practical use, that the head of the bolts 21 positioned close to the main body of the dead end connector 10 is not subject to corona in that the dead end itself tends to shield the heads of the bolts 21. However, the nut 22, and the exposed portion of the bolt 21, extending beyond the nut 22, are not similarly shielded by the dead end 10 and tend to produce corona. This tendency to produce corona is increased by the presence of moisture collecting on the surface of the nut 22 and the exposed bolt 21 portion as well as the main portion of the terminal pad 20'.

Turning now to FIGS. 2 and 3, there is shown a first embodiment of the corona cap fabricated according to the concepts of the invention. Corona cap 40 has a base portion 42 and side walls 44. In this embodiment there are four side walls 44 joined to form an open topped box, the coupling between the base member 42 and the side walls 44, as is shown in FIG. 3, is rounded and filleted so as to provide a smooth continuous surface. Similarly, the side walls 44 are joined as shown in FIG. 2 in smooth filleted corners. The presence of any rough edges on the corona cap will increase the potential gradient at that particular point and will increase the possibility of corona. Stand off supports 46 are connected to the side walls 44, approximately centrally of each one of the side walls 44. Stand off supports 46, as shown in FIG. 3, permit the corona cap 40 to be somewhat removed from the surface of the connector 26, or terminal pad 20, when installed to provide for the drainage of any moisture collected within the corona cap 40 and thus minimize potential gradient bulid-up within the cap.

Centrally disposed within the corona cap 40 is an additional support 48 having an aperture 50 therethrough. As is better seen in FIG. 3, the aperture 50 within the support 48 extends through the entire support 48 and is counter bored as at 52. The counter boring 52 will permit the head of a fastener, employed to bolt the corona cap 40 to the terminal pad 20, or connector 26 to be recessed below the surface of the corona cap 40 eliminating a further point for the formation of corona. Counter boring 52 terminates in a shoulder 54 against which the head of the fastener (not shown) will rest thereby holding the corona cap 40 to the terminal pad 20 or the tap line connector 26. -As is shown in FIG. 4, the corona cap 40 has been bolted to the terminal pad 20 and now provides a smooth continuous surface over the otherwise exposed nut 22 and exposed bolt 21 thread present in FIG. 1. The relationship between the corona cap 40 and the nut 22 and exposed thread of the bolt 21 is shown in FIG. 5 Corona cap 40 has been bolted by means of a bolt 56 passed through the aperture 50 and the support 48, with its head resting upon the shoulder 54 within the counter bored area 52. An additional threaded hole 58 has been provided in the terminal pad 20 for the receipt of the bolt 56. Bolt 56 will provide for the secure fastening of the corona cap 40 to the terminal pad 20.

Turning now to FIGS. 6 and 7, a further embodiment of the corona cap constructed in accordance with the concepts of the invention is shown. The main portion of the corona cap 40 is the same as that described with reference to FIG. 2. However, in this embodiment thin stand off supports 60 are provided at the junctures of each of the side walls 44.

Referring now to FIG. :8, a typical arrangement of a bus bar 70 at a substation, or distribution unit, with a tap line 72 is shown. In such an arrangement neither the bus bar 70 nor the tap line 72 will be protected by a mass similar to that which protects the heads of the bolts 21 in FIG. 1. Thus it is essential that corona caps 40 be applied to both sides of the coupling to protect both the heads of the bolts 21 and the nuts 22 and the exposed thread portions. Such an arrangement is shown in FIG. 8 wherein corona caps 40 have been applied over the bolts and nuts and have been coupled by bolts; such as bolt '56, to the bus bar 70 and tap line connector 72. A tapped hole, similar to that shown as 58 in FIG. 5, will be placed within the tap line connector 72 to receive the bolt to hold the corona cap 40 to the tap line connector 72.

In FIG. 9 a further alternative arrangement of the corona cap 80 either to the terminal pad 20 or tap line cepts of the invention is shown. In this arrangement the corona cap 80 is constructed of a base member 82 and two side walls 84. The remaining two sides of the corona cap are left open. Stand off supports 86 may be provided either at the extreme ends of the side walls 84 or in the center portion thereof. Additional support is given by means of the support 38 which is provided with an aperture therethrough and a bolt head receiving shoulder, similar to that described with reference to FIG. 5. A bolt will be passed through the support 88 to anchor the corona cap 80 either to the terminal pad 20 or tap line connector 26 as is required.

It has been found that shielding on all four sides of the corona cap is not essential and that merely the provision for a continuous smooth surface, over the nut 22 and bolt 21 of FIG. 1, is suflicient. The corona cap constructed in accordance with FIG. 9 is lighter in weight and similar to manufacture than that described with reference to FIGS. 2 and 3, provides the minimal amount of shielding material which otherwise might cause the unwanted collection of moisture and the retaining of heat produced in the coupling.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiments it will be understood that various omissions and substitutions and changes of the form and details of the devices illustrated in their operation may be made by those skilled in the art, without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A corona shield for preventing corona at the juncture of high potential conductors comprising: a base member; four side members extending in planes away from said base member; a plurality of fillets, one for each side member, said fillets each coupled between said base member and one of said side members to provide a smooth, continuous transition between said base member and said side members; four standoff supports, one standoff support coupled to the center of each one of said side members, and extending beyond them to prevent contact between said side members and said high potential conductors and a fastener receiving means below the surface of said base member whereby a fastener placed in said fastener receiving means to fasten said corona shield to said conductor junction remains below said base member surface.

2. A corona shield as defined in claim 1, wherein said fastener receiving means comprises an additional standoff support coupled to said base member, said additional standoff support having an aperture therethrough and a counterbored shoulder below the surface of said base member.

References Cited UNITED STATES PATENTS 964,969 7/ 1910 Hesterhagen 17492 X 1,972,616 9/ 1934 Austin. 2,434,572 1/ 1948 Mankin 174127 X FOREIGN PATENTS 533,150 12/1921 France. 376,553 5/ 1964 Switzerland.

LARAMIE E. ASKIN, Primary Examiner US. Cl. X.R.

222 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,458,646 Dated Julv 29, 1969 lnventofl E L Eldridqe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 63, delete "either to the terminal pad 20 or tap line" and insert constructed in accordance with the con- Column 4, line 15, delete "similar" and insert simpler SEALED 9 DEG 2 u 1969 (SEAL) Attest:

mdLLFletcher Ir. Ed WILLIAM E. 50mm, .112. Attestmg officer Oommissioner of Patents 

